718 
DR. WYVILLE THOMSON ON HOLTENIA. 
rudely square meshes (Plate LXXI. fig. 1) ; very early, however, the stars begin to appear 
by the accumulation and radiation of several of the large spicules at one point, where 
they send all their azygous branches dipping into the sponge in a sheaf (Plate LXXI. 
fig. 3 a). The osculum is very distinct at the summit of the sponge from the first, and 
very early the coronet of upright spicules may be detected rising round its edge. The 
oscular cavity is at first somewhat irregular in form, and its walls are very imperfect 
and open. The spicules of the sarcode of the young sponges do not differ in any essen- 
tial particular, either in form or position, from those of the adult. The characteristic 
spicules (Plate LXXI. figs. 13 & 15) occur ranged as in the adult along the shafts and 
branches of the spicules of the outer and oscular walls. The ‘ amphidisci ’ also occur, 
although not in large numbers. These latter did not seem even to have attained their 
full numerical proportion in a young Holtenia three centimeters long which we dredged 
later in the season off the North of Scotland. One example is figured (Plate LXXI. 
fig. 15) of a regular hexradiate feathered spicule from the young sponge (Plate LXXI. 
fig. 3). This is the characteristic spicule of the sarcode of the netted lid of the genus 
Aphrocallistes. It might easily occur as an abnormal spicule in Holtenia , simply by 
the symmetrical development of the other half of the shaft of the ordinary feathered 
spicule of the outer wall (Plate LXXI. fig. 14) ; but as a species of Aphrocallistes was 
common on the same ground, I am by no means sure that one of its spicules may not 
have got accidentally entangled in the young Holtenia. 
All the young Holtenice in their earlier stages have a beard consisting of a single 
pencil of long spicules passing out together through one of the meshes of the outer wall, 
in the centre of the narrow (inferior) end of the sponge, exactly opposite the centre of 
the osculum. The fascicle consists of from twenty to thirty of the long simple spicules 
and four or five of the bihamate spined spicules (Plate LXXI. fig. 9). At this stage it is 
difficult to distinguish Holtenia , except under the microscope by the form of the spicules, 
from Hyalonema of the same age. Hyalonema seems to retain this embryonic character 
through life, the single original sheaf becoming enormously enlarged, while in Holtenia 
the fascicles are indefinitely multiplied. Young Holtenice from 20 to 30 mtn in length are 
hispid with the finely serrated spicules (Plate LXXI, fig. 19) which pass out singly and 
quite irregularly through the meshes of the wall. The sponge-substance is very loose, 
and the cavities, which afterwards become symmetrical, are at first irregular and very 
large in proportion to the size of the sponge. The long spicules of the beard fascicle do 
not remain in a single sheaf within the sponge-body, but spread round the osculum, 
and appear to rise from different parts of the sponge-substance, even close to the sponge- 
wall. They only approach to pass out of the sponge together. 
On the 16th of August, and on the 7th of September, 1869, Her Majesty’s Ship 
‘ Porcupine’ visited almost precisely the same spot where the specimens of Holtenia 
were dredged in 1868 from the ‘Lightning.’ With finer weather and much better 
appliances we were this year much more successful ; we got abundance of specimens of 
Holtenia Carpenteri , of various sizes and ages, and many examples of the other vitreous 
